This project involves the application of recombinant DNA and immunochemical technologies to isolate and study cDNA clones of mRNAs specifically important to particular regions of the central nervous system. Using improved substractive hybridization procedures, we have isolated more than 150 cDNA clones of mRNAs expressed in cerebral cortex but not detectable in cerebellum; some of these clones have been partially characterized. Because most of these mRNAs are as abundant in hippocampus and caudate nucleus as in cerebral cortex, are present at much lower levels in diencephalon structures and are not detectable in either brain stem or cerebellum, the concept of a telencephalon-enriched battery of genes has emerged. The complete structures of the mRNAs showing the most interesting distributions will be determined by DNA sequence analysis and the encoded proteins will be studied for relationships to proteins whose sequences are known. Immunological reagents will be generated to identify and localize the protein in tissue extracts and in thin sections. To acquire functional information, we will use the "anonymous" genes identified in this study to make new mutant mice affected in cortical function. Variants of the mouse analogues of these genes with a selectable marker inserted within their protein coding regions will be introduced by transformation into embryonic stem cells. Transformants will be screened for site specific integration (homologous recombination) by PCR. Embryonic stem cells heterozygous for such putative null mutations will be reintroduced into mice and germ line recipients will be bred to homozygosity. The phenotypes of mice homozygous for the disrupted versions of the genes will be analyzed to give an indication of the genes' function. As pilot studies, the genes for somatostatin and CCK will be disrupted. In related studies, the cellular phenotype of a mouse already identified to be deleted for one of the neuron- specific genes we have characterized by not grossly neurologically defective will be determined.